1. Field of the Invention
The present invention relates to a lens apparatus capable of performing a manual focus operation and an autofocus operation and a focus operation device for performing the manual focus operation, in particular, a lens apparatus including a rotary operation portion for the manual focus operation and a focus operation device for performing the manual focus operation.
2. Description of the Related Art
A broadcast television camera conventionally has a manual focus mode and an autofocus mode for focusing and is used by switching a focus mode between the manual focus mode and the autofocus mode as needed. The manual focus is an absolute position control which basically includes a one-to-one relation between a focus position and a physical position of an operation portion to be operated by an operator. The operation portion includes a regulation member for limiting the operation range of the operation portion. The autofocus does not need to perform the absolute position control which requires an absolute rotational position of the operation portion. Therefore, when the focus mode is switched from the autofocus mode to the manual focus mode, the focus position moves so as to correspond to the physical position of the operation portion. Thus, a relative relationship between the focus position and a lens position is not maintained to result in a focus error.
Therefore, in order to enable smooth switching from the autofocus mode to the manual focus mode without generating discomfort in the focus operation, the regulation member is required to limit the range of operation according to the position of the lens so as to correspond to a state at the time of switching to the manual focus mode.
Japanese Patent Application Laid-Open No. H02-131208 discloses an electronic ring provided in place of the regulation member. The electronic ring is configured so as to be rotatable by 360 degrees and to generate a focus driving signal by rotational movement. When the electronic ring reaches a limit end of the operation, a load is applied to the electronic ring by a piezoelectric actuator in a thrust direction to lock the electronic ring so as to correct the range of operation.
Japanese Patent Application Laid-Open No. 2000-111783 discloses a focus controller including a stopper pin for limiting the range of operation. The stopper pin is provided on a gear to drive a motor so as to maintain a relative relationship between the position of an operation portion and a lens position.
According to the related art disclosed in Japanese Patent Application Laid-Open No. H02-131208 described above, however, when a user instantaneously performs a reversal operation from a close end or an infinite end in the opposite direction, the release of locking of the piezoelectric actuator is not performed quickly enough. As a result, the reversal operation is inhibited.
According to the related art disclosed in Japanese Patent Application Laid-Open No. 2000-111783, when the focus operation is limited not to one revolution but to multiple revolutions, the motor is disadvantageously increased in size or a structure is complicated to follow an operation speed of the user (to maintain the relative relationship). As a result, it is conceivable that the maintenance of the relative relationship itself cannot be achieved.
Moreover, when a conventional endless operation ring is used, an allowable range of operation cannot be known. As a result, operability is degraded.